1. Field of the Invention
This invention relates generally to a system and method for estimating vehicle roll rate and roll angle and, more particularly, to a system and method for estimating vehicle roll rate and roll angle using vehicle suspension sensors and a 1 degree-of-freedom roll model.
2. Discussion of the Related Art
It is known in the art to detect a potential vehicle rollover using differential braking control, rear-wheel steering control, front-wheel steering control, or any combination thereof. A vehicle roll estimation system may receive vehicle dynamics information from various sensors, such as yaw rate sensors, lateral acceleration sensors and roll rate sensors, to determine the proper amount of action to be taken to detect a potential vehicle rollover. A balance typically needs to be provided between estimating the vehicle roll motion and the vehicle yaw motion to provide the optimal vehicle response. Thus, it is usually necessary to detect certain vehicle conditions to provide the roll detection.
Potential vehicle rollover can be provided to vehicle drivers or can be mitigated by activating adequate chassis control systems with knowledge of vehicle roll stability conditions. Vehicle rollover warning or avoidance systems, therefore, will show satisfactory performance if the roll stability conditions are actively known to the systems. To precisely identify vehicle roll stability conditions, it is advantageous to know the vehicle's roll rate and roll angle since they are the most important states in vehicle roll dynamics.
Several methods have been developed in the art to estimate the roll angle and roll rate information using vehicle sensor measurements. One known technique uses a roll rate sensor together with other vehicle information, such as vehicle speed, steering wheel angle, yaw rate and lateral acceleration, to estimate the roll angle. Another known technique uses a variety of angular rate sensors and accelerometers to estimate the roll angle. All of the known methods require roll rate sensors that can measure the roll rate directly. However, roll rate sensors are not standard vehicle equipment and can be expensive.